A multi-axis accelerometer and a multi-axis angular rate sensor which are small in size and has high reliability are desired by electronics industries, automobile industries, machine industries, and the like.
To cope with the demand, a capacitive type accelerometer is widely used as a multi-axis accelerometer. The capacitive type accelerometer is arranged such that a proofmass is connected to anchor units disposed at several positions on a substrate through springs, and the offset of the proofmass generated by an acceleration applied to the proof mass is detected by the change of a capacitance between a comb-teeth shaped electrode disposed to the proofmass and a comb-teeth shaped electrode fixed to the substrate.
Further, there is also proposed a structure similar to the multi-axis accelerometer as a multi-axis angular rate sensor (for example, JP-A H6-123632 (KOKAI)). More specifically, a proofmass is connected to anchor units disposed at several positions on a substrate through springs, and an alternate voltage is applied between a comb-teeth shaped electrode disposed to the proofmass and a comb-teeth shaped electrode fixed to the substrate. Then, the proofmass is excited by electrostatic force, and the offset of the proofmass generated by Coriolis force applied to the proofmass is detected by the change of a capacitance between the comb-teeth shaped electrode disposed to the proofmass and the comb-teeth shaped electrode fixed to the substrate. This type of the electrostatic type angular rate sensor is widely used.
In general, the sensor described above making use of the change of the capacitance has a disadvantage in that it is difficult for the sensor to process a signal because a formed capacitance is very small although the sensor has an advantage in that a manufacturing cost is low.